51
PRELIMINARY
2 Theory of Operation (continued)
2.2 DC Auxiliary Power Circuit (continued)
2.3 Auxiliary Power Failure Detection
Located at NH-SYS-M board (System MCU and Control Circuit)
Located at NH-SYS-P board (Auxiliary Power for System, Detect Circuit for Voltage and Current)
Located at NH-SYS-M board (System MCU and Control Circuit)
+12VP is from AC auxiliary power and +12VB is from DC auxiliary power. During AC mode, +12VP and +12VB should both be live. If one or
both of them fails, MCU can detect auxiliary power failure through AUXFAIL (71) (low active).
(a) The input of DC auxiliary power circuit is from positive battery.
(b) MCU detects the “on” key (on LCD board) status through KEY-ON(21)
(c) When AC auxiliary power circuit is activated and battery is present, AUXON (64) is high and DC auxiliary power circuit will be on.
(d) If AUXOFF (44) is high during backup mode, DC auxiliary power will be off.
RM2 2
AUX-ON
RM2 6
AUX-OFF
(64)
(44)
AUXON
AUXOFF
RM4 3
K-ON
RM4 2
5VS
CM2 4
G1
(21)
KEY_ON
QP8
RP 1 8
RP 1 9
RP 2 0
DP11
QP9
RP 2 1
RP 2 2
RP 2 3
DP12
G1
G1
+12VS
+12VS
+12VB
+12VP
RP 2 4
QP10
G1
ZDP5
ZDP6
AUX-FAIL
RM3 5
AUX-FAIL
RM3 4
5VS
(71)
CM2 3
G1
AUXFAI L
